This application relates generally to a system and method for electromagnetically launching payloads such as projectiles, launch vehicles, spacecraft, aircraft, missiles, rockets, or the like, and more particularly relates to an electromagnetic launcher, an electromagnetic launch system and a method for electromagnetically launching such payloads that utilizes magnetic levitation, stabilization and propulsion, employing a transverse direct current magnetic field generated in superconducting cables extending along a launch tube.
Electromagnetic launch systems typically are capable of accelerating payloads such as projectiles, launch vehicles, spacecraft, aircraft, missiles or rockets, for example, to high velocities. Electromagnetic launching of such payloads has the major advantage of minimizing or even eliminating the need to carry fuel and rocket motors for propulsion and stabilization of the payloads, as is particularly the case with missiles and rockets. Launching projectiles electromagnetically can also achieve much higher muzzle velocities for the projectiles than is possible with other conventional methods, such as artillery.
One prior art electromagnetically energized railgun system is known that utilizes nesting and segmenting of primary rails in combination with augmenting rails and crossover bar conductors, and an inductorless single power supply arrangement. The railgun system includes a launch tube containing two or more electrically conducting rails along which a projectile-carrying sabot slides. Acceleration force is generated when a current is passed up through one rail, through an armature, which physically contacts the rail, and down another rail, creating a magnetic pressure that pushes the sabot along the launch tube. However, such railgun systems typically have a maximum practical launch velocity achievable with railguns and is on the order of 3 kilometers per second, which constrains the range of projectiles launched on earth to only a few hundred miles, and is far below the velocity needed to achieve orbit for a payloads, which is on the order of 8 kilometers per second. Furthermore, because railguns commonly require that an armature physically contact the rails, the rails must be replaced on a regular basis due to the extreme mechanical stresses and erosion present with this technology.
A conventional coil gun is also known that utilizes an electromagnetic projectile accelerator including stationary coils aligned along an axis of a launch tube for acceleration of a magnetic projectile down the launch tube, by sequentially energizing each individual coil as the projectile approaches to electromagnetically pull or push the projectile along the launch tube. While projectiles launched by such coil guns need not contact any rails on the inside of the launch tube, as is the case with railguns, such coil guns also have a limited maximum practical velocity, due to the need to sequentially and precisely switch large currents through the series of coils on short (sub-microsecond) time scales. This constraint limits the maximum practical velocities and masses of the launched projectiles.
A space tram (Powell and Maise, 2001, U.S. Pat. No. 6,311,926 B1) for launching a spacecraft from earth into outer space is also known that utilizes a launch tube that is magnetically suspended, with an inlet on earth and an elevated outlet. The spacecraft includes superconducting loops, and when the launch tube is evacuated, the payload is propelled through the launch tube by magnetic levitation to achieve escape velocity for reaching outer space, due to magnetic interaction between the superconducting loops on the spacecraft and an alternating current (AC) wave flowing in non-superconducting, normal metal loops embedded in walls of the launch tube.
While such magnetic levitation or maglev launch systems based on the magnetic acceleration of spacecraft equipped with superconducting loops can achieve orbital speeds of 8 kilometers per second or greater with potentially much lower launch costs than rockets, such conventional maglev launch systems are difficult to scale down to smaller systems such as those optimized for launching small satellites on the order of 100 kilograms, and typically requires specialized power conditioning equipment to generate the necessary AC current required to accelerate the vehicle. While such magnetic levitation systems can potentially be used for launch systems with launch tubes less than 50 km long providing moderate accelerations of less than 500 m s2 (50 g), such magnetic levitation systems are typically prohibitively expensive for shorter launch systems necessarily requiring higher accelerations, and typically require that spacecraft launched in this manner to have sufficient superconductor cables to carry large currents (500,000 to 1,000,000 amps), which can be prohibitively costly for the launch of small payloads on the order of 100 kg.
Furthermore, such maglev launch systems that use high current superconducting loops on the payload being launched typically require a complex travelling AC current wave in the rails on the walls of the launch tube that pushes on the superconducting magnets on the payload to accelerate the payload. The frequency of the AC power wave must be finely adjusted and controlled using DC to AC inverters to increase its frequency as the velocity of the payload being launched increases. In addition, only a short section of the launch tube where the payload being launched moves along the launch tube can be energized. As the payload being launched moves along the launch tube, the travelling AC power wave is switched off from the presently energized section that the payload is leaving, and is switched onto the next section into which the payload is moving.
It would therefore be desirable to provide an electromagnetic launcher and a system and method for electromagnetically launching a payload such as a projectile, launch vehicle, spacecraft, aircraft, missile, rocket, or the like, that involves no confining mechanical contact and friction of the payload with a launch tube wall, to allow launching many such payloads at extremely high velocity without damage to the launch tube wall or the payloads being launched.
It would also be desirable to provide such an electromagnetic launch system and method that does not require high current superconducting loops on such a payload, in order to greatly simplify and reduce costs of the design and manufacture of the projectile, launch vehicle, spacecraft, aircraft, missile, rocket, or other similar payload to be launched, and allowing the launching of much smaller and lighter such payloads than is possible with conventional maglev launch systems.
It would also be desirable to provide such an electromagnetic launch system and method in which the power conditioning system required for accelerating such payloads is much simpler and less costly than power conditioning systems required for maglev launch systems that use high current superconducting loops on the projectile or launch vehicle.
It would also be desirable to provide such an electromagnetic launch system and method that utilizes a simple DC current stationary power source, with the current flowing from DC rails mounted to an interior tube wall through a moving payload to be launched. It would also be desirable to provide such an electromagnetic launch system and method in which the complete length of the DC rails along the launch tube is energized with the DC current that flows into the payload being launched across small gaps between the rails and the payload being launched via plasma arcs or via conducting brushes, for example, eliminating the requirement for expensive, complex electronic switches to control the frequency and activation location of the current needed by other maglev launch systems that employ superconducting loops on the payload being launched and a traveling AC current wave. The present invention meets these and other needs.